These include well-established serological biomarkers, such as the CA15-3 assay, detecting mucin MUC1 glycoprotein used for breast cancer (126–130), the CA125 assay, which detects the circulating mucin MUC16 in ovarian cancer (131, 132), and the prostate-specific antigen (PSA), which is used to detect prostate diseases (133, 134). The gene discussed is KLK3; the disease is breast cancer.